Based on the G100UL fuel leak thread what's your position?

[Marc_B]

1 hour ago, Paul Thomas said:

I'd say a thread for field reports should be created

I tried to do that but most of those who have tried G100UL haven’t said much. We’ve had I believe 4 or so who have posted that they’ve fueled with G100UL (outside of the two with paint issues).

And to be clear, the intention of the thread was only to have field reports of use rather than debate/discussion, speculation, etc. I still think this would be helpful to share what works, how to mitigate paint staining and to help show where more data is needed  

 

[T. Peterson]

The reason this debate is so emotionally charged is not because G100UL is good or bad, but because it appears that this is going to be forced on the consumer by government fiat. The fact that some have a serious concern with the fuel certainly exacerbates the issue, but if no one felt they would be forced into it, most of the heat would dissipate. People would not be fuming on Mooneyspace, they just wouldn’t buy the fuel.

@GeeBee mentioned that it is probably time to field test this new fuel, and I agree. The FAA has anointed it and so let the market forces test it. Let the FBO’s decide what they want to sell. They don’t have to offer two choices. If they only have one tank or simply just want to deal with one fuel, their choice. If they think G100UL is their path to better profitability than so be it. If the next FBO at a neighboring airport feels different and sticks with 100LL, that’s their business choice. Let the market decide. 
Much heat has been leveled against GAMI which I think is misdirected. The real culprit is a weak  government that bowed to a special interest using junk science. I utterly reject the notion that we must bow and genuflect to the inevitable “Tsunami” coming our way. Especially with the coming change of administration, there may be a real window of opportunity to roll back some of this government overreach. Even if nothing changes, there is yet 5 years (if I correctly understand the mandate) to field test this fuel. If it proves to be the greatest thing since sliced bread, we will all race to buy our STC. But if the only place it sells is where state governments have prematurely banned 100LL, is that not in itself a pretty good indicator of where the field testing is going? And if the fuel proves to be a disaster that would certainly spark a further movement to delay the mandate. Per chance by that time there would be a real drop-in fuel or even some adult leadership at the EPA.

I do understand there is a real sense of urgency on the part of California owners as it certainly appears the steamroller is gearing up. I am very sorry for that and I can only encourage you to enlist the help of any sympathetic voices that may remain in your government.

 

[ragedracer1977]

4 hours ago, George Braly said:

Sabre,

You may be right on the regulatory issue.  I have not researched that. 

But what you stated explicitly contradicts the Bendix document.     

And - - regardless of whether or not your regulatory interpretation is correct:

Failing to comply with that 1980 Service Bulletin - -  absent a LOT of explicit log book documentation and warnings to the owner(s) of the aircraft - - the failure to comply with a  SB relating to the fuel system - - would likely subject the mechanic to some serious liability in the event the fuel servo failed and resulted in an accident. 

George

I’m somewhat taken aback by this answer.

this suggests the possibility that you may not have tested certain things because you believed SBs are mandatory and thus extremely unlikely a part that precedes the SB could still be in service. 

[MikeOH]

@T. Peterson

Best post of thread.  Well summarized, well done.

[Kelpro999]

Has anyone discussed how the fuel changes with time in our tanks? I see more planes set on the ramp for what seems like years then one day it’s in the pattern. 100LL pulls it off on a regular basis but… 

  I venture to say most GA aircraft have atmosphere vents breathing with the slightest temp difference throughout every day and night. 
 Could get serious if that change makes a runway feel short.

[GeeBee]

7 hours ago, Kelpro999 said:

Has anyone discussed how the fuel changes with time in our tanks? I see more planes set on the ramp for what seems like years then one day it’s in the pattern. 100LL pulls it off on a regular basis but… 

  I venture to say most GA aircraft have atmosphere vents breathing with the slightest temp difference throughout every day and night. 
 Could get serious if that change makes a runway feel short.

Or never get to the runway. There is one candidate fuel out there that uses ETBE. Which has ethanol. Ethanol when used in boats that like airplanes sometimes sits for a while was a disaster. It destroyed fiberglass fuel tanks but worse it corroded aluminum tanks. This is because over time, ethanol fuels under go "phase separation" and the ethanol absorbs a bunch of water. That mixture sinks to the bottom of the tank and starts corroding it. Many of a boat owner has arrived at their boats to find gallons of fuel leaked into the bilge from aluminum tanks, several times the thickness of our Mooney tanks. Go down any marine supply store's "chem aisle" and you will see additives such as "Marine Sta-Bil" and Star Tron which are designed to prevent phase separation. 

One can only imagine the repair bill for a corroded wet wing like our Mooney's. The factory would at least make a brisk business of cutting new wing skins. Would you rather reseal your tanks for G100UL, or replace skins before you reseal your tanks with ethanol?

[Pinecone]

15 hours ago, Sabremech said:

Why should we have to accept this additional maintenance and cost to run a different fuel? None of this is cheap! it sure seems that the mission continues to make flying only possible for the wealthy! Why not design and manufacture a fuel that is a direct drop in replacement that does NOT require additional maintenance and cost to any owner? That should be the priority to not add additional cost going forward! If the new fuel costs a little more per gallon to get it out in the field, that’s understandable. To require me to reseal my poorly maintained 50 + year old tanks because those schmuck mechanics over the years couldn’t do it right is ridiculous. Stop blaming mechanics for this mess. Stop blaming mechanics for not adhering to some obscure letter from the FAA that says we should be replacing o-rings with Viton or Flourosilicone every chance we get. This mess isn’t on us and it shouldn’t be. There’s problems with this fuel for the guy on a budget. Those who don’t have a budget could care less and are over zealous fans of this product because it doesn’t impact their wallet like it does most of us little guys who just want to enjoy the same freedom of flying. @George Braly, good job on making an effort and progress on your unleaded fuel but please stop discounting the little guy on a budget. Paint stains or paint loss matter to us! Don’t brush us off like AOPA does. 

Two different things.

EPA and state and local governments are going after 100LL.  We have been burning it for decades on an exemption.  Knowing that the exemption was not permanent.

So, right now you have one choice for a UL aviation fuel for the entire fleet.  If 100LL is banned, you have two choices.  Use G100UL or not fly.

If it was so easy to develop a fuel that is total drop in, without ANY issues, don't you think that someone would have done so????   The government has thrown millions of your tax dollars at the problem.  How many solutions came out of that?

[Pinecone]

11 hours ago, Paul Thomas said:

Re-arguing the same point with no new information is taking away from the actual data presented by users (that includes the youTube video) and the manufacturer. We're getting to the point where people are arguing just to argue and throwing in red herring just hoping to score a point.

The people I want to hear from the most are G100UL users. I want to hear the good, the bad, and the ugly but it's getting drowned by the noise made from members on both side of the isle that just want to argue. I'd say a thread for field reports should be created, but I'd imagine it would get taken over by the same members.

I get it, both sides have dug in and are deeply passionate about their positions but the tone and quality of the arguments are disappointing. Let's keep it fun and educational.

We have heard from some.  And silence from others.  Remembering that people are more likely to complain than praise, there are a few issues with a few airplanes.

And NO reports of any issues with O-rings.

[George Braly]

10 hours ago, Kelpro999 said:

Has anyone discussed how the fuel changes with time in our tanks? I see more planes set on the ramp for what seems like years then one day it’s in the pattern. 100LL pulls it off on a regular basis but… 

  I venture to say most GA aircraft have atmosphere vents breathing with the slightest temp difference throughout every day and night. 
 Could get serious if that change makes a runway feel short.

Kelpro,

Sometime in the 2011 time frame,  Continental asked us to send them four drums of G100UL avgas for Continental to test in Mobile. 

~ 3 years later, I called them and asked them for a copy of their test report.   "We have not had time to test your fuel."

After a rather surprised moment - -  I then asked them where the fuel was stored.  "In an open shed here in Mobile."

Then I had them ship it back to us to use for long term storage stability testing.   I think I still have one drum of that that has never been opened! 

The fuel was still "conforming"  to the specification when it was returned.   It had last a small amount of vapor pressure, but that is normal for any fuel. 

George 

[George Braly]

5 hours ago, GeeBee said:

Or never get to the runway. There is one candidate fuel out there that uses ETBE. Which has ethanol. Ethanol when used in boats that like airplanes sometimes sits for a while was a disaster. It destroyed fiberglass fuel tanks but worse it corroded aluminum tanks. This is because over time, ethanol fuels under go "phase separation" and the ethanol absorbs a bunch of water. That mixture sinks to the bottom of the tank and starts corroding it. Many of a boat owner has arrived at their boats to find gallons of fuel leaked into the bilge from aluminum tanks, several times the thickness of our Mooney tanks. Go down any marine supply store's "chem aisle" and you will see additives such as "Marine Sta-Bil" and Star Tron which are designed to prevent phase separation. 

One can only imagine the repair bill for a corroded wet wing like our Mooney's. The factory would at least make a brisk business of cutting new wing skins. Would you rather reseal your tanks for G100UL, or replace skins before you reseal your tanks with ethanol?

The Swift 100R  has about 25% ETBE.   But the ethanol fraction of the ETBE is supposed to be controlled by an ASTM production spec for ETBE so that it is not more than 1% of the ETBE.   So the amount of ethanol in Swift 100R should be relatively small.   [However, we have seen some very peculiar material compatibility issues with 25% ETBE fuel chemistries.]

The basic Swift Patents suggest a fuel chemistry that would be  ~ 25% ETBE & 70% "high grade aviation alkylate"  and ~ 3-5% butanes or iso-butanes for vapor pressure.   Swift claims the "supercharge" rating is > than 130.   But that is only obtained at a F/A ratio that is "off scale" higher than any actual F/A ratio that is used by our engines.   The ASTM D909 laboratory supercharge test data for one similar fuel chemistry reflects a supercharge rating of only around 115 (rather than ~ 130 for 100LL and > 150 for G100UL avgas) at the full power / full rich Fuel-Air ratios typical of our fleet of high powered engines. 

ETBE is potentially useful for aviation gasoline, but only if one is able to "manage" or "mitigate"  ETBE's own set of problems.   The detonation characteristics are such that it is  - -  (in our judgment, and based on our test data of  ETBE fuel blends we have made IAW the reported Swift 100R fuel chemistry and then tested in back to back testing with 100LL and G100UL avgas on our test stand) - -  rather unlikely that   Swift 100R could be used for any of the high powered engines without significant "adjustments" to the engines, such as retarding the timing or reducing the redline CHTS and imposing limits on the IAT,  or likely, some combination of all of the above.   

But we may be "missing something" in our evaluation and analysis.    Always open to new information. 

 

[Sabremech]

2 hours ago, Pinecone said:

Two different things.

EPA and state and local governments are going after 100LL.  We have been burning it for decades on an exemption.  Knowing that the exemption was not permanent.

So, right now you have one choice for a UL aviation fuel for the entire fleet.  If 100LL is banned, you have two choices.  Use G100UL or not fly.

If it was so easy to develop a fuel that is total drop in, without ANY issues, don't you think that someone would have done so????   The government has thrown millions of your tax dollars at the problem.  How many solutions came out of that?

I don’t need a history lesson. We’re all keenly aware of what’s on the horizon for 100LL. 
I never inferred that it was going to be an easy process. We would only have one choice if the government chose to ban 100LL today. That’s not going to happen. Other companies are working on a solution / alternate as well. I for one think Shell has the best potential to supply the system as it’s currently being supplied for 100LL now. That’s going to be determined at the FBO or airport management level and not you or I.

The government has thrown trillions of our tax dollars at solutions looking for a problem. Looks like we have plenty of problems out of those tax dollars. 

[George Braly]

1 hour ago, Sabremech said:

I don’t need a history lesson. We’re all keenly aware of what’s on the horizon for 100LL. 
I never inferred that it was going to be an easy process. We would only have one choice if the government chose to ban 100LL today. That’s not going to happen. Other companies are working on a solution / alternate as well. I for one think Shell has the best potential to supply the system as it’s currently being supplied for 100LL now. That’s going to be determined at the FBO or airport management level and not you or I.

The government has thrown trillions of our tax dollars at solutions looking for a problem. Looks like we have plenty of problems out of those tax dollars. 

As I understand the situation - - Shell currently does not produce one drop of 100LL anywhere in the United States.    I think it still produces some 100LL - - maybe in Holland.

Again - - there are a lot of "facts"  associated with this 30 year process.   It takes a "deep dive" into both the current and past refining structure / infrastructure and a similar deep dive into the (so far) unproductive "industry"  (ASTM / FAA / Taxpayer / PAFI / EAGLE) history to fully appreciate how we got to where we are today.   

[GeeBee]

2 hours ago, George Braly said:

The Swift 100R  has about 25% ETBE.   But the ethanol fraction of the ETBE is supposed to be controlled by an ASTM production spec for ETBE so that it is not more than 1% of the ETBE.   So the amount of ethanol in Swift 100R should be relatively small.   [However, we have seen some very peculiar material compatibility issues with 25% ETBE fuel chemistries.]

The basic Swift Patents suggest a fuel chemistry that would be  ~ 25% ETBE & 70% "high grade aviation alkylate"  and ~ 3-5% butanes or iso-butanes for vapor pressure.   Swift claims the "supercharge" rating is > than 130.   But that is only obtained at a F/A ratio that is "off scale" higher than any actual F/A ratio that is used by our engines.   The ASTM D909 laboratory supercharge test data for one similar fuel chemistry reflects a supercharge rating of only around 115 (rather than ~ 130 for 100LL and > 150 for G100UL avgas) at the full power / full rich Fuel-Air ratios typical of our fleet of high powered engines. 

ETBE is potentially useful for aviation gasoline, but only if one is able to "manage" or "mitigate"  ETBE's own set of problems.   The detonation characteristics are such that it is  - -  (in our judgment, and based on our test data of  ETBE fuel blends we have made IAW the reported Swift 100R fuel chemistry and then tested in back to back testing with 100LL and G100UL avgas on our test stand) - -  rather unlikely that   Swift 100R could be used for any of the high powered engines without significant "adjustments" to the engines, such as retarding the timing or reducing the redline CHTS and imposing limits on the IAT,  or likely, some combination of all of the above.   

But we may be "missing something" in our evaluation and analysis.    Always open to new information. 

 

Personally based upon experience in the marine industry, I don't want any ethanol anywhere near my airplane. I am fortunate in Georgia I can purchase 91 octane non-ethanol fuel. The difference in stability is astonishing. My fear and correct me if I am wrong is the ethanol will "phase separate" and while the percentage per gallon is small in fresh fuel, because of the specific gravity when it phase separates it accumulates at the bottom of the tank in gross proportions that lead to tank corrosion.

[Sabremech]

1 hour ago, George Braly said:

As I understand the situation - - Shell currently does not produce one drop of 100LL anywhere in the United States.    I think it still produces some 100LL - - maybe in Holland.

Again - - there are a lot of "facts"  associated with this 30 year process.   It takes a "deep dive" into both the current and past refining structure / infrastructure and a similar deep dive into the (so far) unproductive "industry"  (ASTM / FAA / Taxpayer / PAFI / EAGLE) history to fully appreciate how we got to where we are today.   

Hi George,

From what I’m reading Shell has fuel available in Europe for testing, etc. It makes me wonder if they’re going to go the EASA route for certification and then bring it to the US where the FAA gives a blanket approval. I should have gone that route on my STC’s as the FAA automatically accepts them but the other way around, nope, spend more money with EASA for approval. 

[donkaye]

On 1/8/2025 at 9:56 AM, MikeOH said:

What's the highest percentage of G100UL in your tank that you have used?  As I recall you have been mixing with 100LL.

About 50%.

[George Braly]

3 hours ago, Sabremech said:

Hi George,

From what I’m reading Shell has fuel available in Europe for testing, etc. It makes me wonder if they’re going to go the EASA route for certification and then bring it to the US where the FAA gives a blanket approval. I should have gone that route on my STC’s as the FAA automatically accepts them but the other way around, nope, spend more money with EASA for approval. 

Please share with me any information you may have on that subject of Shell in Europe doing testing on a new fuel formulation.   There is no hint of that within the EAGLE / PAFI group to the best of my knowledge .

Further, just before Christmas, I was in Europe and I meet with several of the senior leaders in the European general aviation world and they had no knowledge of any activity for a high octane unleaded fuel being developed anywhere within the European Union or in the United Kingdom. 

 

[exM20K]

On 1/5/2025 at 1:59 PM, redbaron1982 said:

With this story of "the infrastructure can handle only one fuel type at any given airport" the only way for G100UL has a chance to succeed is by banning 100LL

It also happens to be true.  We are in the discovery phase of replacing the 30 year old underground dual tank, dual pump setup at my Illinois joint. Approximate quote? $550-850,000 for 2x8000 gallons. 8000/4000 above ground is the better part of $300,000. 
 

At the low end, 3000 gallons above ground: $160,000.  That is a big nut for an FBO or county.

Above ground also incurs a lift charge for delivery, and delivery has a flat-rate dispatch fee.  Together, these add $0.15 - $0.30 cents to fuel cost.

-dan

 

 

[IvanP]

14 hours ago, GeeBee said:

 Would you rather reseal your tanks for G100UL, or replace skins before you reseal your tanks with ethanol?

Neither. I would like to be able to purchase fuel that does not damage my aicraft as is without requirimg me to spend tens of thousands of dollars. 

[GeeBee]

I don't think the chemistry is with you.

 

[Sabremech]

3 minutes ago, GeeBee said:

I don't think the chemistry is with you.

 

You don’t know that. It’s not 2030 and there are other companies working on an alternative fuel. Give it a rest. 

[GeeBee]

I think if CEH wins their motion to enforce the consent decree (and they likely will), 2030 is irrelevant. 

[Sabremech]

9 minutes ago, GeeBee said:

I think if CEH wins their motion to enforce the consent decree (and they likely will), 2030 is irrelevant. 

I don’t give a darn about California and doubt anything they do will change the 2030 target for the other 49 states. As I stated before, give it a rest. 

[George Braly]

28 minutes ago, Sabremech said:

You don’t know that. It’s not 2030 and there are other companies working on an alternative fuel. Give it a rest. 

 

Please identify each sponsor of an Unleaded High Octane candidate replacement for 100LL who has not publicly stated or acknowledged that their candidate UL fuel will require modifications of the engines in order to pass detonation test requirements.

 

 

[Kelpro999]

15 hours ago, GeeBee said:

Ethanol

 Living in CA and currently maintaining well over twenty carburetors in various toys, I’m unfortunately well aware of the adverse effects of alcohol. Sealed fuel injection systems not really a problem. Marine Sta-bil is my friend but still has its limitations.

[Kelpro999]

11 hours ago, George Braly said:

~ 3 years later, I called them and asked them for a copy of their test report.   "We have not had time to test your fuel."

Hello George,

 This statement seems to imply the drums remained sealed and suffered no ill effects from evaporation or absorption. My concern with aircraft is most if not all fuel tanks have far greater evaporation surface v depth that’s open to atmosphere and consequently breathing through the vents. Is this something that has been studied? 
 Like I mentioned earlier, some sit forever then all of a sudden heading down the runway. Just curious what your thoughts might be.